G-CSF regulation of CXCR4 mRNA synthesis. (A) Appearance of CXCR4-related bands evaluated by Western blotting. 32Dcl3 cells were cultured for 3 and 6 days with IL-3 alone or with IL-3 plus G-CSF. (B) CXCR4 mRNA levels were measured by quantitative PCR. 32Dcl3 cells were cultured for 3 days with IL-3 alone or IL-3 plus G-CSF. The results reflect the means of 3 experiments; the error bars reflect SD of the mean (*P < .05). (C) Kinetic of CXCR4 mRNA decay was measured by quantitative PCR. 32Dcl3 cells were cultured for 1 to 6 hours in the presence of actinomycin-D. The results are from a representative experiment and reflect the means of triplicate determinations; the error bars represent SD of the mean. (D) Effects of G-CSF on CXCR4 mRNA decay measured by quantitative PCR. 32Dcl3 cells were cultured for 1 hour or 2 hours with or without actinomycin-D in the presence of IL-3 alone or with IL-3 plus G-CSF. The results (expressed as percentage of CXCR4 mRNA in cells cultured with IL-3 alone) reflect the means of triplicate determinations; the error bars represent SD of the mean.